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authorNils Hoppmann <niho@linux.ibm.com>2023-10-09 16:40:48 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-10-19 23:08:54 +0200
commitf05befe5c441b37ff1e033a01b6695a9a64d7d9c (patch)
tree189594f6f1359282ebaa2cf9b09ffc3931b36229 /net/smc
parente4f2611f07c87b3ddb57c4b9e8efcd1e330fc3dc (diff)
net/smc: Fix pos miscalculation in statistics
[ Upstream commit a950a5921db450c74212327f69950ff03419483a ] SMC_STAT_PAYLOAD_SUB(_smc_stats, _tech, key, _len, _rc) will calculate wrong bucket positions for payloads of exactly 4096 bytes and (1 << (m + 12)) bytes, with m == SMC_BUF_MAX - 1. Intended bucket distribution: Assume l == size of payload, m == SMC_BUF_MAX - 1. Bucket 0 : 0 < l <= 2^13 Bucket n, 1 <= n <= m-1 : 2^(n+12) < l <= 2^(n+13) Bucket m : l > 2^(m+12) Current solution: _pos = fls64((l) >> 13) [...] _pos = (_pos < m) ? ((l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m For l == 4096, _pos == -1, but should be _pos == 0. For l == (1 << (m + 12)), _pos == m, but should be _pos == m - 1. In order to avoid special treatment of these corner cases, the calculation is adjusted. The new solution first subtracts the length by one, and then calculates the correct bucket by shifting accordingly, i.e. _pos = fls64((l - 1) >> 13), l > 0. This not only fixes the issues named above, but also makes the whole bucket assignment easier to follow. Same is done for SMC_STAT_RMB_SIZE_SUB(_smc_stats, _tech, k, _len), where the calculation of the bucket position is similar to the one named above. Fixes: e0e4b8fa5338 ("net/smc: Add SMC statistics support") Suggested-by: Halil Pasic <pasic@linux.ibm.com> Signed-off-by: Nils Hoppmann <niho@linux.ibm.com> Reviewed-by: Halil Pasic <pasic@linux.ibm.com> Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com> Reviewed-by: Dust Li <dust.li@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/smc')
-rw-r--r--net/smc/smc_stats.h14
1 files changed, 9 insertions, 5 deletions
diff --git a/net/smc/smc_stats.h b/net/smc/smc_stats.h
index 4dbc237b7c19..ee22d6f9a86a 100644
--- a/net/smc/smc_stats.h
+++ b/net/smc/smc_stats.h
@@ -93,13 +93,14 @@ do { \
typeof(_smc_stats) stats = (_smc_stats); \
typeof(_tech) t = (_tech); \
typeof(_len) l = (_len); \
- int _pos = fls64((l) >> 13); \
+ int _pos; \
typeof(_rc) r = (_rc); \
int m = SMC_BUF_MAX - 1; \
this_cpu_inc((*stats).smc[t].key ## _cnt); \
- if (r <= 0) \
+ if (r <= 0 || l <= 0) \
break; \
- _pos = (_pos < m) ? ((l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m; \
+ _pos = fls64((l - 1) >> 13); \
+ _pos = (_pos <= m) ? _pos : m; \
this_cpu_inc((*stats).smc[t].key ## _pd.buf[_pos]); \
this_cpu_add((*stats).smc[t].key ## _bytes, r); \
} \
@@ -139,9 +140,12 @@ while (0)
do { \
typeof(_len) _l = (_len); \
typeof(_tech) t = (_tech); \
- int _pos = fls((_l) >> 13); \
+ int _pos; \
int m = SMC_BUF_MAX - 1; \
- _pos = (_pos < m) ? ((_l == 1 << (_pos + 12)) ? _pos - 1 : _pos) : m; \
+ if (_l <= 0) \
+ break; \
+ _pos = fls((_l - 1) >> 13); \
+ _pos = (_pos <= m) ? _pos : m; \
this_cpu_inc((*(_smc_stats)).smc[t].k ## _rmbsize.buf[_pos]); \
} \
while (0)